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Blum, P.

Publications and source records attributed to Blum, P..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Solar-Driven Neutral Density Waves

Interstellar neutral hydrogen atoms flowing into the solar system are attracted by the solar gravitational force, repelled by solar hydrogen Ly-alpha radiation pressure, and are ionized, primarily, through charge exchange with the solar wind protons. The solar cycle variation of the radiation pressure causes the net central solar force to fluctuate between attraction and repulsion resulting in the modulation of the neutral hydrogen density about the usual time independent model. The calculation presented here shows that the time dependent downstream density is strongly modulated by a large number of travelling neutral density waves. The waves possess a continuous range of wavelengths as is to be expected for a Maxwellian gas subjected to several eleven year cycle variations during its journey through the solar system. The amplitudes of the density modulation were found to be quite large. The backscattered glow was found to depend on the position of the detector and the phase of the solar cycle. At the most favorable condition a deviation of the order of 25% from the time dependent glow might be observed.

Blum, P.↗
NASA NTRS1992

Vacuum ultraviolet detection of the VLISM-heliosphere interaction

As the neutral components of the interstellar gas flow through the heliosphere their spatial distribution is modified by charge exchange with the solar plasma, photoionization, and radiation pressure. The deep space probes Pioneers 10/11 and Voyagers 1/2 have provided an opportunity to investigate this distribution through VUV observations of the heliospheric glow. Since the interactions of the inflowing neutrals with the heliosphere depend on both space and time it is particularly useful to have multiple spacecraft observations. Pioneer 10 is in the downstream region of the inflowing interstellar breeze at 50 AU while Pioneer 11 and Voyager 2 are upstream at about 30 AU. Voyager 1 is also upstream at about 40 AU but at a heliographic latitude of + 30 deg. Both temporal and spatial effects are expected to be quite different for the upstream and downstream regions. Some of the recent VUV data and its implications with respect to the heliospheric structure will be presented.

Judge, D. L.↗
NASA NTRS1974

A representation of Jacchia's thermospheric models in spherical harmonic functions

The Jacchia models are represented in terms of spherical harmonic functions. This representation has the advantage of ease of comparison with other global theoretical and empirical models that use this mathematical form. Furthermore, it is analytic, continuous, and has continuous derivatives all over the globe. The representation of the exospheric temperatures shows clearly the amplitudes of the various periodic terms and uses relatively few constants. An example of a similar representation for the total mass density at a particular height and level of solar activity is given as well.

Blum, P.↗
NASA NTRS1973

A representation of Jacchia's thermospheric models in spherical harmonics

The Jacchia models are represented in terms of spherical harmonic functions. This representation has the advantages of ease of comparison with theoretical and other observational models and data, mathematical analyticity and relative simplicity. The symmetry properties of the models are emphasized by this representation and some physical characteristics like the increase of the amplitude of the diurnal density variation with decreasing solar activity become more apparent.

Blum, P.↗
NASA NTRS1972

The physics of the neutral upper atmosphere.

Particular attention is given to models of the upper atmosphere that deal with the diurnal variation and the latitudinal density dependence. The upper atmosphere is considered as essentially an ideal gas, or rather a weakly ionized plasma, where physical and chemical processes of considerable complexity take place. The final goal for the theoretical models of the upper atmosphere is to derive the time and space dependence of the physical quantities density, composition, temperature, pressure, and state of motion by theoretical considerations from basic physical assumptions. Questions of the dynamics of the upper atmosphere are discussed together with one- and two-dimensional models of the upper atmosphere, three-dimensional models, the geomagnetic effect, and the semiannual density variation.

Blum, P.↗
NASA NTRS1971

Rock sampling

A method for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The method involves cutting grooves in the rock surface to provide a grouping of parallel ridges and subsequently machining the ridges to provide a powder specimen. The machining step may comprise milling, drilling, lathe cutting or the like; but a planing step is advantageous. Control of the particle size distribution is effected primarily by changing the height and width of these ridges. This control exceeds that obtainable by conventional grinding.

Blum, P.↗
NASA NTRS1971

Rock sampling

An apparatus for sampling rock and other brittle materials and for controlling resultant particle sizes is described. The device includes grinding means for cutting grooves in the rock surface and to provide a grouping of thin, shallow, parallel ridges and cutter means to reduce these ridges to a powder specimen. Collection means is provided for the powder. The invention relates to rock grinding and particularly to the sampling of rock specimens with good size control.

Blum, P.↗
NASA NTRS1968

Preparing rock powder specimens of controlled size distribution

Apparatus produces rock powder specimens of the size distribution needed in geological sampling. By cutting grooves in the surface of the rock sample and then by milling these shallow, parallel ridges, the powder specimen is produced. Particle size distribution is controlled by changing the height and width of ridges.

Blum, P.↗